Recs.
Updated
Salt is free and open-source and written in Python, there is also an enterprise edition.
VMware acquired SaltStack and its products in October 2020.
SpecsUpdate
Pros
Pro Fast execution of commands
Salt works around a Salt master which has multiple agents (Salt minions) that have a persistent connection to the master. Because of this persistent connection, commands to the master are fast to reach the minions. Furthermore, the minions also save various data to the cache in order to make execution faster.
When compared against other tools to run the same actions, Salt almost always completes the actions in significantly less time.
Pro Friendly and open community
Salt has an impressive welcoming and active community of users. There are user groups all over the world (Stockhom, Silicon Valley, Paris, and lots more), and an active live chat.
Cons
Con Security issues
Salt uses the PyCrypto package to roll out its own AES implementation. Though unfortunately there have been some security issues reported.